Method of recovering fibrous material from a scrap of a sheet-like fibrous structure containing a polyvinyl alcohol resin binder treated with titanic acid

ABSTRACT

A METHOD OF RECOVERING FIBROUS MATERIAL FROM A SCRAP OF A SHEET-LIKE FIBROUS STRUCTURE CONTAINING A POLYVINYL ALCOHOL BINDER TREATED WITH TITANIC ACID, WHICH COMPRISES TREATING A SHEET-LIKE FIBROUS STRUCTURE SELECTED FROM PAPERS AND NON-WOVEN FABRICS WHICH HAVE BEEN FORMED BY EMPLOYING AS BINDER A POLYVINYL ALCOHOL RESIN SOLUBLE IN WATER OF NOT OVER 95*C. AND IN WHICH THE POLYVINYL ALCOHOL RESIN BINDER HAS BEEN TREATED WITH TITANIC ACID, WITH AN AQUEOUS SOLUTION OF A MINERAL ACID CONTAINING HYDROGEN PEROXIDE.

United States Pat .111:

US. Cl. 162-6 9 Claims ABSTRACT OF THE DISCLOSURE A method of recovering fibrous material from a scrap of a sheet-like fibrous structure containing a polyvinyl alcohol binder treated with titanic acid, which comprises treating a sheet-like fibrous structure selected from papers and non-woven fabrics which have been formed by employing as binder a polyvinyl alcohol resin soluble in water of not over 95 C. and in which the polyvinyl alcohol resin binder has been treated with titanic acid, with an aqueous solution of a mineral acid containing hydrogen peroxide.

This invention relates to a method of recovering fibrous material advantageously and with ease from a scrap of a sheet-like fibrous structure, such as paper and non-woven fabric, containing a polyvinyl alcohol resin binder treated with titanic acid, from which type scrap of a sheet-like fibrous structure the recovery of fibrous material is impossible in accordance with conventional methods comprising boiling the scrap in an aqueous solution because the polyvinyl alcohol resin used as binder has been made insoluble in either water or hot water by the titanic acid treatment.

More specifically, this invention relates to a method of recovering fibrous material from a scrap of a sheet-like fibrous structure containing a polyvinyl alcohol resin binder treated with titanic acid, which comprises treating a sheet-like fibrous structure selected from papers and non-woven fabrics which have been formed by employing as binder a polyvinyl alcohol resin soluble in water of not over 95 C. and in which the said polyvinyl alcohol resin binder has been treated with titanic acid, with an aqueous solution of a mineral acid containing hydrogen peroxide.

There has been known a method of forming a sheet-like fibrous structure such as paper and non-woven fabric from fibrous material with the use as binder of a polyvinyl alcohol resin soluble in water and hot water.

There has been also known a method of insolubilizing such waterand hot water-soluble polyvinyl alcohol resin which comprises preswelling a solid polyvinyl alcohol in the form of film, fiber, granule or powder, preferably by contacting it with an aqueous medium, and treating the preswelled solid polyvinyl alcohol with a solution of a water-soluble, chlorine-free titanium compound such as titanyl sulfate, titanium nitrate, titanium lectate, titanium acetate, titanium oxalate, titanium hydroxyacetate, glyceryl titanate, and other titanating agents (see US. patent specification No. 2,518,193).

Further, as a result of our researches it was found that an aqueous mineral acid solution of a-titanic acid possesses excellent properties as such titanating agent solution.

The titanic acid treatment referred to in this invention means a treatment of a polyvinyl alcohol resin with a 3,5973% Patented Aug. 3, 1971 solution of one or more of the above mentioned titanating agents for insolubilizing the polyvinyl alcohol resin.

We made researches on the preparation of water-resistant paper and non-woven fabric from fibrous material such as natural fibers, synthetic or artificial fibers and blends thereof with the use as binder of a polyvinyl alcohol resin treated with titanic acid. We also made researches on methods of recovering the above fibrous material from scraps of such sheet-like fibrous structures, for instance, chips formed during the finishing of the structures or during the processing of them into secondary products, or used products of such sheet-like fibrous structures, and reusing such scraps for the preparation of sheet-like fibrous structures without throwing them away in waste.

However, it is impossible to dissolve the binder resin by boiling it in water or an aqueous solution, because the binder resin has been treated with titanic acid. Accordingly, it is impossible to recover the fibrous material used for the formation of the fibrous structure in a reusable state namely, in the form of the original fiber, by such conventional means.

Therefore, with a view to developing treating liquors which would make this recovery possible, we furthered our researches and as a result we arrived at the knowledge that aqueous solutions of a mineral acid containing hydrogen peroxide are excellent treating liquors in use for said recovery. It was quite a surprising discovery that although a sufficient recovery cannot be attained by a single use of hydrogen peroxide or an aqueous solution of a mineral acid, an aqueous solution of a mineral acid containing hydrogen peroxide exhibits an excellent ability of recovering the fibrous material. The mineral acid referred to in this invention includes sulfuric acid, hydrochloric acid, nitric acid, etc.

Accordingly, a primary object of this invention is to provide a method of advantageously recovering from a scrap of paper or nonwoven fabric containing a polyvinyl alcohol resin binder treated with titanic acid, fibrous material constituting said paper or non-woven fabric by a simple operation employing a treating recovery liquor which is cheap and comes easily to hand.

Other objects and advantages will be made apparent by the description given below.

The material to be treated in this invention is a scrap of paper or non-woven fabric which has been formed from a fibrous material with the use as binder of a polyvinyl alcohol resin capable of being dissolved in water of not over 95 C., preferably not over 90 (1., especially preferably not over C., and in which the said polyvinyl alcohol resin binder has been treated with titanic acid during or after the preparation of paper or nonwoven fabric.

As the fibrous material constituting paper or non-woven farbic there are cited natural fibers derived from animal, plant and mineral resources such as pulp, linter, cotton, hemp, wool, silk and asbestos, preferably cellulose type natural fibers; artificial fibers such as viscose rayon and acetate rayon; synthetic fibers prepared from fiber-forrning synthetic resins such as polyvinyl chloride, polyvinyl alcohol, formalized polyvinyl alcohol, polyacrylic acid esters, polyamide, polyacrylonitrile, polypropylene and polyvinylidene chloride; and blends of these fibers.

The fiber denier and fiber length of the fibrous material constituting paper or non-woven fabric are those usually adopted in the art of the manufacture of paper and nonwoven fabric, and one skilled in the art can easily understand within what range they fall.

Of course, the material to be treated in this invention, namely a sheet-like fibrous structure containing a polyvinyl alcohol resin binder treated with titanic acid may contain, besides said binder and fibrous material, any of 3 various additives whose incorporation into paper or nonwoven fabric has been known, such as paper-reinforcing materials, e.g., starch, cationic starch, guayule gum and polyacrylamide; sizing agents, e.g., rosin, gelatin, starch and alkyl ketene dimer; and coating materials, e.g., kaolin, sericite, clay and halocite.

In the preparation of the sheet-like fibrous structure, the binder may be used in an aqueous solution form or in a solid state, for instance, a fibrous, flaky or powdery state. The technique of forming paper or non-woven fabric from fibrous material with the use of a binder is well known. Therefore, a detailed description of this technique is omitted herein. However, it must be noted that in the fibrous structure to be treated in this invention the polyvinyl alcohol resin used as binder has been made insoluble into water and hot water by the titanic acid treatment during or after the preparation of the fibrous structure to such an extent that a mere boiling in water cannot result in disintegration of the fibrous material.

In the method of this invention, a scrap of paper or nonwoven fabric containing as binder a polyvinyl alcohol resin which has been subjected to the above mentioned titanic acid treatment, namely, a polyvinyl alcohol resin binder made insoluble into water and hot water, is contacted with an aqueous solution of a mineral acid containing hydrogen peroxide.

The contact may be conducted by an optional means as far as it given a sufficient contact between the aqueous solution of a mineral acid containing hydrogen peroxide and paper or non-woven fabric. For instance, there may be adopted dipping, spraying, coating, preferably repeated coating, and other similar treatments. Optionally, dipping under agitation may be adopted.

Further, in the method of this invention, after having conducted the treatment with the aqueous solution of a mineral acid containing hydrogen peroxide, it is possible to carry out an after-treatment comprising washing with water or an alkaline aqueous liquor such as a diluted aqueous solution of an alkali metal hydroxide, an alkali metal carbonate or an alkali metal bicarbonate and an aqueous ammonia, and dipping or boiling in hot water.

The conditions of the tretment with the aqueous solution of a mineral acid containing hydrogen peroxide are variable from considerably mild conditions to considerably drastic ones. For instance, in case the fibrous material to be recovered is relatively weak to the aqueous solution of a mineral acid containing hydrogen peroxide, relatively mild treatment conditions are adopted, and it is preferable to conduct the above mentioned after-treatment according to need. In case the fibrous material to be recovered is sufficiently resistant to the aqueous solution 015 a mineral acid containing hydrogen peroxide, somewhat more drastic treatment conditions may be advantageously adopted.

It will be easily understood that the treatment conditions vary depending on the concentration of the aqueous soluiton of a mineral acid containing hydrogen peroxide, the class of the mineral acid, the contents of hydrogen peroxide and the mineral acid, the treatment temperature and the treatment time, and that the conditions can be suitably controlled.

Generally, as the concentration of the aqueous solution is higher, the content of the mineral acid is higher, the treatment temperature is higher and/ or the treatment time is longer, the treatment conditions become more drastic, and vice versa, the treatment conditions become relatively milder. Of course, the degree of mildness or drasticality in the treatment conditions may be optionally changed by varying combinations of the above mentioned various factors. For instance, even in the case of a fibrous material relatively weak to the aqueous solution of a mineral acid containing hydrogen peroxide, a sufiicient mild treatment may be attained at a considerably high concentration of the aqueous solution if the treatment time is short and the treatment temperature is as low as possible. Further, even in the case of a mild treatment the object of disintegrating the sheet-like fibrous structure can be sufliciently attained by conducting in combination the above mentioned aftertreatment.

In view of the control of the above mentioned treatment conditions, it is possible to adopt the treatment temperature of 20 to C. and the treatment time (the time during which the paper or non-woven fabric is in contact with the treating liquor) of 1 to 60 seconds. In view of the control of the above mentioned treatment conditions in the light fo the above treatment time and temperature, it is usual to adopt the mineral acid concentration of 1 to 200 g. per liter of the treating liquor in the case of sulfuric acid, 0.8 to 150 g. per liter of the treating liquor in the case of hydrochloric acid and 1.3 to 260 g. per liter of the treating liquor in the case of nitric acid, and the hydrogen peroxide concentration of 1 to 50 g. per liter of the treating liquor. In a preferred embodiment, a sulfuric acid concentration of 10 to g./liter, a hydrochloric acid concentration of 7.5 to 75 g./liter or a nitric acid concentration of 10 to g./ liter, and a hydrogen peroxide concentration of 3 to 10 g./liter are adopted. It is preferable that the weight ratio of hydrogen peroxide to the mineral acid in the treating liquor is within a range of 1:1 to 1:20 in the case of sulfuric acid, 1:0.8 to 1:16 in the case of hydrochloric acid, or 121.3 to 1:26 in the case of nitric acid.

By the above mentioned treatment the sheet-like fibrous material has been disintegrated and there is obtained a liquid system in which the fibrous material is dispersed in a state divided into fibers. The fibers can be easily recovered by separating the fibrous material from the liquor in accordance with a customary liquidsolid separation technique, for instance, by filtration or decantation.

An embodiment of combinations of treatment conditions will be now described more specifically.

In case a vinylon paper (composed of 80 parts of modified polyvinyl alcohol difiicultly soluble in water and 20 parts of polyvinyl alcohol soluble in water at 60 C., and having a basic weight of 60 g./m. which has been treated with titanic acid to such an extent that no change in the form is caused to occur by boiling in 100 C. hot water for ten minutes and which has a tensile strength in the wet state of 4.0 kg./l5 mm. is dipped for 10 seconds in a treating liquor containing 10 g./liter of hydrogen peroxide and 100 g./liter of sulfuric acid and maintained at 70 C., the swelling of paper is observed 7 seconds after the initiation of the dipping, and 10 seconds after the initiation of the dipping the paper is disentegrated into fibers. Further, in case the above vinyl paper is dipped into the above treating liquor maintained at 50 C. for 10 seconds, the swelling of the paper is not caused to occur at the completion of the treatment and the paper can be taken out from the treating liquor in the state maintaining its original form. When the so recovered vinylon paper is dipped into hot water after water washing, the swelling is immediately caused to occur, and 10 seconds later the paper is integrated into individual fibers completely.

The method of this invention will be now described by refering to examples.

EXAMPLES 1 AND 2 AND COMPARATIVE. EXAMPLES 1 TO 5 A paper (having a basic weight of 60 g./m. formed of 80 parts by weight of cut fibers of 30% formalized modified polyvinyl alcohol difiicultly soluble in water and 20 parts by weight of a binder of polyvinyl alcohol cut fibers soluble in water at 80 C., which had been treated with titanic acid to such an extent that no change in the form would not be caused to occur by boiling in 100 C. hot water for 10 minutes and had a breakage strength in the wet state of 2.8 km., was treated with hydrogen peroxide-containing aqueous solutions of sulfuric acid indicated in Table I below under the treating conditions indicated in Table I. The results are shown in Table I.

For comparison, Table I also shows the results of comparative examples where the above procedures were conducted in the same manner except using an aqueous solution of hydrogen peroxide or an aqueous solution of a mineral acid alone as the treating liquor.

taining g./liter of hydrogen peroxide and 10 g./1iter of sulfuric acid and maintained at 70 C. After the dip ping treatment the sample was washed with water and dipped in hot water. Just after the dipping into hot water the swelling of the sample was caused to occur, and the sample was disintegrated seconds after the dipping into hot water.

TABLE I Treating liquor Hydrogen Temperature peroxide Mineral acid of treating Treatment concentration concentration liquor C.) (dipping) Example No. g./liter) 1 (g./1iter) l (dipping) time (sec.) Disintegration of paper into fibers in hot water.

Example 1 H202 (10) H1302 (100). 50 10 Disintegrated 5 seconds after initiation of treatment. Comparative Example 1 11202 (10) 50 10 Not disintegrated at all. Comparative Example 2 H2804 (100). 5O 10 Do. Comparative Example 3 H61 (75) 50 10 Do. Comparative Example 4 HNOa (130).-. 50 10 Do. Example 2 H202 (5) E1504 (100)... 50 10 Disintegrated after 7 seconds. Comparative Example 5.--- H; (5) 50 10 Not disintegrated.

1 The value of the concentration is expressed in terms of grams per liter of the treating liquor.

EXAMPLES 3-8 A vinylon paper (formed of 80 parts by weight of 30% formalized modified polyvinyl alcohol fibers difficulty soluble in water and 20 parts of a binder of polyvinyl alcohol fibers soluble in water at 80 C. and having a basic weight of 60 g./m. which had been treated with titanic acid to such an extent that no change in the form would not be caused to occur by boiling in 100 C. hot water for 10 minutes, was used as sample. The titanic acid treated sample paper was dipped into hydrogen peroxide-containing mineral acid aqueous solutions indicatcd in Table II below under the conditions indicated in Table II. Then, the paper was taken out from the treating liquor, washed with water and dipped into 100 What We claim is:

1. A method of recovering fibrous material from a scrap of a sheetlike fibrous structure containing a polyvinyl alcohol binder treated with titanic acid, which comprises treating a sheet-like fibrous structure selected from papers and non-woven fabrics which have been formed by employing as a binder a polyvinyl alcohol resin soluble in water of not over 95 C. and in which the polyvinyl alcohol resin binder has been treated with titanic acid, with an aqueous solution of a mineral acid containing hydrogen peroxide.

2. The method as described in claim 1, wherein the sheet-like fibrous structure is further subjected to a boiling treatment in hot water after the treatment with the aque- (3. hot water, and the disintegration of the paper into 0118 solution of a mineral acid containing hydrogen fibers was examined. peroxide.

TABLE II Hydrogen peroxide Mineral acid Liquid Dipping Example concentration concentration temperature tune (g./l.iter) (gm/liter) C.) (see) Dislntegration in hot water 5 H soi (100 70 10 10 H 5 04 (10 6O 10 Dislntegrated 13 seconds after the initiat on of dipp ng nto hot water. 10 H 804 (l0 50 60 Disintegrated 10 seconds after the initiation of dipping nto hot water. 10 H01 (75) 50 10 Dislntegrated 12 seconds after the initiation of dipping into hot water. 10 HNO; (l30) 5O 10 Disintcgrated 9 seconds after the initiation of dipping into hot water.

1 The paper was completely disintegrated in the treating liquor without being dipped in hot water.

EXAMPLE 9 A paper composed of 80 parts by Weight of viscose rayon and 20 parts by weight of a binder of polyvinyl alcohol fibers soluble in water at 80 C. which had been treated with titanic acid to such an extent that no change in the form would not be caused to occur by boiling in 100 C. hot water for 10 minutes and which had a basic weight: of g./m. was used as sample. This titanic acid-treated rayon paper was dipped for seconds in an aqueous solution containing 10 g./ liter of hydrogen peroxide and 10 g./liter of sulfuric acid and maintained at 50 C. After water washing, the rayon paper was dipped into 100 C. hot water, and after 10 seconds dipping the paper was disintegrated into rayon fibers, which were recovered with the use of a wire-netting of 100 mesh.

EXAMPLE 10 A non-woven fabric composed of 80 parts by weight of 30% formalized polyvinyl alcohol fibers and 20 parts by weight of a binder of polyvinyl alcohol fibers soluble in water at 80 C., and having a basic weight of 70 g./m. was treated with titanic acid. By this treatment, the nonwoven fabric was made to have a tensile strength of 3.0 kg./5 cm. even after boiling in 100 C. hot water for 10 minutes. This titanic acid-treated paper was used as sample and dipped for 60 seconds in a treating liquor con- 3. The method as described in claim 1, wherein the aqueous solution of a mineral acid containing hydrogen peroxide is an aqueous solution of sulfuric acid containing hydrogen peroxide, the sulfuric acid concentration is 10 to grams per liter of the treating liquor and the hydrogen peroxide concentration .is l to 50 grams per liter of the treating liquor.

4. The method as described in claim 3, wherein the weight ratio of hydrogen peroxide to sulfuric acid is in the range of from 1:1 to 1:20.

5. The method as described in claim 1, wherein the aqueous solution of a mineral acid containing hydrogen peroxide is an aqueous solution of hydrochloric acid containing hydrogen peroxide, the hydrochloric acid concentration is 7.5 to 75 grams per liter of i the treating liquor and the hydrogen peroxide concentration is l to 50 grams per liter of the treating liquor.

6. The method as described in claim 5, wherein the weight ratio of hydrogen peroxide to hydrochloric acid is in the range of from 1:08 to 1:16.

7. The method as described in claim ll, wherein the aqueous solution of a mineral acid containing hydrogen peroxide is an aqueous solution of nitric acid containing hydrogen peroxide, the nitric acid concentration is 10 to grams per liter of the treating liquor and the hydrogen peroxide concentration is 1 to 50 grams per liter of the treating liquor.

. a 7 v I 8. The method as described in claim 7, wherein the References (Iited Weight ratio of hydrogen peroxide to nitric acid is in the UNITED STATES PATENTS range of from 1:13 to 1:26.

9. The method as described in claim 1 wherein the 3,248,277 4/1966 Gartner 162-6X treatment with the aqueous solution of a mineral acid 3,407,113 10/1968 Maxwell 162-6 containing hydrogen peroxide is conducted at a tempera- 5 ture of 20 to 90 C. for 1 to 60 seconds. HOWARD CAINE, Prlmary Examlner 

